1. Field
Embodiments relate generally to CTE-matched glasses and more particularly to low- to no-alkali aluminosilicate, borosilicate, and aluminoborosilicate glasses which may be useful in semiconductor-based applications, such as photovoltaics, photochromics, electrochromics, or Organic Light Emitting Diode (OLED) applications.
2. Technical Background
The fusion forming process typically produces flat glass with optimal surface and geometric characteristics useful for many electronics applications, for instance, substrates used in electronics applications, for example, display glass for LCD televisions.
Over the last 10 years, Corning fusion glass products include 1737F™, 1737G™, Eagle2000F™, EagleXG™, Jade™, and Gorilla Glass™. Efficient melting is generally believed to occur at a temperature corresponding to a melt viscosity of about 200 poise (P). These glasses share in common 200 P temperatures in excess of 1600° C., which can translate to accelerated tank and electrode corrosion, greater challenges for fining due to still more elevated finer temperatures, and/or reduced platinum system life time, particularly around the finer. Many have temperatures at 3000 P in excess of about 1300° C., and since this is a typical viscosity for an optical stirrer, the high temperatures at this viscosity can translate to excessive stirrer wear and elevated levels of platinum defects in the body of the glass.
Many of the above described glasses have delivery temperatures in excess of 1200° C., and this can contribute to creep of isopipe refractory materials, particularly for large sheet sizes.
These attributes combine so as to limit flow (because of slow melt rates), to accelerate asset deterioration, to force rebuilds on timescales much shorter than product lifetimes, to force unacceptable (arsenic), expensive (capsule) or unwieldy (vacuum fining) solutions to defect elimination, and thus contribute in significant ways to the cost of manufacturing glass.
In applications in which rather thick, comparatively low-cost glass with less extreme properties is required, these glasses are not only overkill, but prohibitively expensive to manufacture. This is particularly true when the competitive materials are made by the float process, a very good process for producing low cost glass with rather conventional properties. In applications that are cost sensitive, such as large-area photovoltaic panels and OLED lighting, this cost differential has been large enough to make the price point of LCD-type glasses unacceptable.
Competing with the cost constraints for is the continuing drive to make new technologies, like PV, competitive with existing power production methods, e.g., hydro, coal, nuclear, wind, etc., in the power generation industry. To do so, in addition to cost, manufacturers are looking at conversion efficiency, device lifetime, and efficiency degradation—design challenges that need to be addressed to make PV a viable alternative. Soda lime glass has been a common substrate for most PV panels because of its low cost. However, soda lime glasses are not ideal for PV modules, especially CdTe-based thin film PV modules as sodium can cause problems with efficiency and device lifetime. Further, soda lime glasses can have sodium release issues that occur due to environmental conditions. These problems can lead to delamination issues and reduced efficiency. Clearly, there is still an unmet need to find glass compositions that provide optimal substrates for thin film PV devices.